Radicular leg pain
Most often, hnp or herniated/ruptured disc, causes irritation of one of the nerves that go into an extremity (arm or leg).
Your discs are just like jelly-donuts. When you rip the outside of your donut and the jelly leaks out, that's a herniated disc. That jelly is the most irritating substance in the human body, and it will chemically inflame many structures in the spine. Injections work well.